This invention relates to leak-resistant automotive
battery.
BACKGROUND OF THE INVENTION
One of the major technological innovations in the last
two decades has been the development of a maintenance-free
battery for automotive applications and this technology is
now widely used in the battery industry world-wide. However,
since most of the automotive batteries contain free
electrolyte, the hazards of acid leakage still persists
particularly during battery handling, that is during
transportation and charging. Acid spillage or leakages are
undesirable, as they can cause burns, and the corrosion of
battery terminals and the related electrical systems in the
automobile. As a result, there is a definite preference Ln
the market for a safe, leak-proof battery which can be
handled easily without posing these hazards. In view of
this, a small percentage of automotive batteries are being
converted to leak-proof, valve regulated type assembled
batteries with AGM (Absorptive Glass Mat) separators,
especially for the premium range of vehicles.
However, valve regulated automotive batteries are
substantially more expensive to manufacture. Furthermore,
the flooded battery designs are known to have certain
technical advantages in comparison to the acid-starved, VILLA
(Valve Regulated Lead Acid) designs. In spite of substant:.al
cost penalties as well as certain technical limitations, the
trend appears to be towards the valve regulated types mainly
due to the need for a safe, leak-proof maintenance-free
battery. For example, most of the future designs for a 35V
automotive battery are of the VRLA type, assembled with A3M
separators.
It is clear from the above description that further
technical developments are required to make leak-proof/leak
resistant automotive batteries of flooded variety. These
designs are still predominantly used all over the world
primarily due to their lower cost as well as the ease of
manufacturing.
Hitherto, there have been many attempts to develop a
leak-resistant automotive battery with free electrolyte using
a specially designed battery cover. In this context, some cf
the important innovations which have taken place in the last
20 years are being discussed below:
US Patent No. 4,348,466 published on September 7, 198 2
(assigned to Varta Batterie Ltd., Willowdale, CA) discloses
an anti-spill arrangement for a liquid electrolyte battery
which consists of a large rectangular chamber with an inlet
in communication with the respective battery cell and an
outlet in communication with the vent to the atmosphere. The
chamber and the associated passages have sufficient volume to
retain the electrolyte flow when the battery is tipped o:r
rotated. Furthermore, the chamber arrangement is such that
the contained level of electrolyte remains spaced from the
outlet. When the chambers and the passages are filled with
electrolyte, an air lock is developed which prevents
additional flow of electrolyte from the cell to the chamber
and the passage configuration. The notable point in this
patent is that large chambers and passage configuration allov
for substantial amount of electrolyte to flow into th2
battery cover and thereby increase the likelihood o:
electrolyte spilling into the venting area, ultimately
causing leakage from the battery system, especially if the
battery is vibrated or agitated. Furthermore, this patem;
does not provide leak protection in the inverted position o::
the battery.
German Patent No. 4,216,563 published on November 24th
1993 (assigned to VB Autobatterie GmbH) discloses a double-
cover type construction having a chamber associated with each
cell. Each chamber is properly sized such that when the
battery is tilted, only a limited amount of acid from the
respective cell enters the collection chamber which the
chamber can accommodate. In the inverted position however, a
substantial amount of electrolyte flows out from the cells
into the cover, thus increasing the risk of electrolyte:
leaking from the battery.
In US Patent No. 5,380,604 to Hampey et. al. (published,
on January 10, 1995) and US Patent No. 5,424,146 to Lir.
(published on June 13, 1995), similar configurations have
been seen. The leak-resistant battery cover comprises of two
parts, i.e. an upper lid and a lower lid, having chambers
associated with each cell. Each chamber has guides for
controlling the flow of acid. The guides are so designed
that in any position of the housing, even when resting on one
of the side walls, the acid within the chambers remains below
the critical level, and above which the acid flows into the
spark arrestor. However, a significant amount of electrolyte
is allowed to flow into the respective cover which increases
the possibility of acid leakage when the battery is vibrated
or agitated. Also, there is little or no protection against
electrolyte leakage when the battery is inverted.
US Patent No. 5,683,830 published on November 4, 199''
and US Patent No. 5,843,593 published on December 1, 1998
(assigned to Douglas Battery Manufacturing Company, USA)
disclose a leak resistant battery cover in two parts. The
battery cover provides a labyrinth of passages - providing a
path from each cell vent to the atmospheric vent. The
labyrinth provides a portion of each path above the level
which the electrolyte attains when the battery is tilted or
rotated 90° from an upright position.
German Patent No. EP 0 639 862 Bl published on
September 18, 1996 (assigned to VB Autobatterie GmbH)
discloses a multi-cell battery having a central gas venting
system integrated in the battery cover and incorporating a
gas collecting duct and providing in the side wall of the
cover a depression which is connected by a side duct to the
collecting duct and an insert is provided in the depression.
The insert contains a porous frit closing the gas duct which
is connected to the cover in an air-tight manner. The frit
is so arranged in the insert that, its lower edge is always
above the level of the acid return flow.
The patents described above are generally based on
relatively complex configurations of a battery cov^r which
comprises of two parts, i.e. an upper lid and a lower lid and
the upper lid is then sealed with the main cover either
ultrasonically or by heat sealing. These designs of battery
cover are relatively expensive and more complex at the
manufacturing stage. Clearly, there is a need for a simple,
leak resistant cover without having any adverse effect on its
cost competitiveness.
The present invention is aimed at making a flooded
automotive battery leak-resistant in all directions, for a
considerable length of time, say in excess of 12 hrs, i.e.
when the battery is rotated at 90° on the front face, back
face, either of the side faces or in a completely inverted
position starting from a normal upright position.
Description of the present invention
Accordingly, the present invention provides a multi-cell
leak-resistant automotive battery comprising:
a housing containing cells having filling plugs;
a battery cover heat-sealed to the upper open end of
said housing and having filling holes overlying
respective said cells;
terminals mounted on said battery cover and connected to
said cells;
and optionally charge indicator mounted on said battery
cover;
characterised in that,
at least one partition wall is provided in the battery
cover to divide the battery cover into at least two vent
chambers, each vent chamber overlying a set of said
cells, to prevent flow of electrolyte from one set of
cells to an adjacent set of cells when the battery is
tilted;
a common vent line in the battery cover to connect the
spaces above the cells in each set of cells, each said
common vent line being sealed at one end and connected
at its other end through each said vent chamber to ore end of a
respective parallel vent line, and each said parallel
vent line having at its other end a vent cap assembly
which permits escape of vented gases from the cells in
each set.
The common vent line in each vent chamber is sealed at
said one end by means of a vent stop extending through the
battery cover into the vent hole of the first cell of e^ich
set.
The vent cap assembly comprises a vent cap fitted to
said other end of the parallel vent line, and a gas filter
attached to the vent cap for allowing the vented gas to
escape.
The vent cap has a vent hole provided on the inlet side
of the vent cap , a first vertical hole extending upwardly to
the outer periphery of the vent cap and in communication with
said vent hole, a helical path for passage of vented gases
provided on the outer periphery of the vent cap and connected
said vent hole, a helical path for passage of vented gases
provided on the outer periphery of the vent cap and connected
at one end to said first vertical hole, a second hole
connected to said helical path at the other end of the
helical path, said second vertical hole extending downwards
to the centre at the exit side of the vent cap so as to be in
communication with said filter.
The gas filter is preferably a water-repellc.nt
microporous gas filter. The microporous filter may have a
grain size of about 70 microns. The gas filter fitted into
the vent cap is provided with a filter cover having a hoLe
for escape of vented gas.
In a preferred embodiment, each vent chamber is provided
with a chamber cover press-fitted to it, said vent chamber
and chamber cover being heat sealed to the battery cover.
The present invention provides a multi-cell lea<
resistant automotive battery having a side/central ga;3
venting arrangement wherein the central vent line in tho
battery cover is blocked in the middle, corresponding to the
middle partition of the battery container. Effectively, this
creates two isolated battery compartments with cells. In a
preferred embodiment, the battery has six cells, with 3
cells in each battery compartment.
Whereas the batteries with side venting arrangement
exhibit leak resistant properties when rotated 90° on the
front/back face or completely inverted - resulting from an
air-lock, this type of construction is generally prone to
acid leakage when rotated 90° along the side face in the
direction of the side vent line. This weakness in the
central/side gas venting designs has been fully overcome in
the present invention.
The invention will now be described with reference to
preferred embodiments shown in the accompanying drawings,
wherein -
Figs. 1 and 1A show front elevational view and plan view of
an automotive battery according to the present invention;
Figs. 2 and 2A show rear elevational view and side view of
the battery of Fig. 1;
Fig. 3 shows sectional plan view of the battery along
section line A-A in Fig. 1;
Fig. 3A shows an enlarged and detailed view of the circled
part X shown in Fig. 3;
Fig. 3B shows an enlarged and detailed view of the circled
part Y shown in Fig. 3;
Fig. 4 shows sectional view along line B-B in Fig. 1A;
Fig. 4A shows a detail of the vent chamber cover (item 23) in
Fig. 4;
Fig. 5 shows an isometric view of vent cap assembly used in
the battery according to the present invention;
Fig. 5A shows side elevational view of the vent cap assembly
of Fig. 5;
Fig. 5B shows sectional view of the vent cap assembly alor.g
line C-C in Fig. 5A;
Fig. 6 shows the battery of Fig. 1A tilted by 90° to lie en
one of its shorter sides;
Fig. 7 shows the battery of Fig. 1A tilted by 90° to lie on
its back side; and
Fig. 8 shows the battery of Fig. 1A tilted by 90° to lie on
its front side.
From Figs. 1 and 1A, it can be seen that the battery has
a housing l having a cover 2. Cells Cl to C6 are provided Ln
the housing 1. Each cell is provided with a filling plug I.
The filling plugs 3 are not provided with any venting hol'2S
and they are flush fitted tightly in the battery cover wi:h
the help of 0 ring seals. These filling plugs 3 are fluuh
with the top surface of the battery cover. Optionally, a
sunk-in lifting handle 4 may be provided so as to be flush
with battery cover 2 as shown in Fig. 1A. A charge indicator
CI, is provided on the cover 2.
In Fig. 2, it can be seen that each side wall of the
housing is provided with a honey comb structure general]y
indicated by reference numeral 5. This is an optional
feature. Such honey comb structure of the side wall prevents
bulging of the housing 1. Fig. 2 also shows hinge 6 on which
the handle 4 is hinged to be operable.
Fig. 3 shows top sectional view of the battery according
to the present invention taken along section line A-A in Fig.
1. Some of the novel features of the present invention are
shown in this Figure as well as in Figs. 3A and 3B. The
battery cover has filling holes 8-13 over respective cells
C1-C6. A central blockage wall 7 is provided to block the
common/side vent line through filling holes 8-13 within the
battery cover to form vent chambers 22. Thus one vent line
VL1 connecting filling holes 8, 9 and 10 is separated by the
wall 7 from the other vent line VL2 connecting filling holes
11, 12 and 13. These two common vent lines are connected to
respective parallel vent lines 14 and 15. One parallel vent
line 14 is thus connected on one side to the vent chamber
formed by the common vent line VL1 connecting the filling
holes 8 to 10 of cells CI to C3 and parallel vent line 15 is
connected on one side to the vent chamber formed by the
common vent line VL2 connecting the filling holes 11 to 13 of
cells C4 to C6. Each of the parallel vent lines 14, 15 has
at its other end 14', 15' a cylindrical hole provided with a
vent cap assembly 16.
Fig. 3A shows how the end 8' of vent hole 8 overlying
cell CI is closed by a vent stop 17 extending into battery
cover 2. This vent stop is provided also on the end 13' of
vent hole 13 overlying cell C6. By this, vent lines VL1 and
VL2 are sealed on one side and connected to the parallel vent
lines 14 and 15 on other side.
The vent chamber 22 formed over each set of cells C1-C3
and C4-C6 is provided with a chamber cover 23 shown in Fig. 4
and in greater detail in Fig. 4A. Both the chamber and
chamber cover are heat-sealed with the underside of the
battery cover 2, thus creating a closed loop for the
gas/electrolyte within each set of three cells. Vent cap
assembly 16 for venting the vent chamber 22 over each set of
cells C1-C3 and C4-C6 will now be described with reference to
Figs. 3B, 5, 5A and 5B.
As already described, each parallel vent line 14, 15 has
one end connected to the respective common vent line VII,
VL2. At the other end, each parallel vent line 14, 15 has a
cylindrical hole 14' and 15' respectively in which a vent cap
assembly is fitted.
The vent cap assembly 16 (fig.5) comprises a vent cap 18
fitting into the cylindrical hole 14', 15' provided at said
other end of each parallel vent line. The vent cap is
preferably push-fitted in the cylindrical hole. At the inl2t
end, the cap has a vent hole 18' in communication with a
first vertical hole 24 extending upwards to the outer
periphery of the vent cap 18. A helical path 25 is provided
on the outer periphery. At one end, the helical path :.s
connected to the first vertical hole 24. At the other end of
the helical path, a second vertical hole 26 extends
downwards into the centre of the cap 18. A water-repellant
microporous gas filter 19 is provided at the outlet end of
the vent cap and lies adjacent to hole 26. At the end of the
filter 19, remote from the vent cap 18, there is provided a
filter cover 20 having a hole 21 (fig.5B) for escape cf
vented gas which exits through hole 26 and is filtered ty
filter 20. The filter cover locks the filter to the body 16
of the vent cap 18.
When any gas is vented through the parallel vent line 14
or 15, it exits through the cylindrical hole in that line to
the vent cap. The vented gas then traverses vertically up
through hole 24 and moves along the helical path 25 and then
descends downwards to the center of the vent cap 18 before
coming into contact with the gas filter 19 as
diagrammatically shown in Fig. 5. The gas permeated through
filter 19 exits through the opening in the filter cover 20.
The filter cover 20 is preferably a plastic cover. Thus the
filter is prevented from coming into contact with any dust on
the exposed outer surface of the parallel vent line.
The common vent lines VL1 and VL2 extending over the
cells C1-C3 and C4-C6 are closed at one end by means of vent
stop 17. However for the escape of gases, parallel vent
lines 14 and 15, connected to common vent lines VLl and VL2
at one end and closed at the other end are provided. The
parallel vent lines are provided in the battery cover to
connect vent chamber 22 to cylindrical hole at the exit and
of each parallel vent line 14 and 15. A specially designed
vent cap assembly 16 is push-fitted into the cylindrical
opening and has a water-repellant microporous gas filter.
The filter cover is locked into the vent cap. Thus the need
for additional heat sealing or ultrasonic sealing operation
can be dispensed with.
Vent chamber 22 on each set of cells has a chamber cover
23 press-fitted to it and then heat sealed with the underside
of the battery cover. So, no separate heat sealing operation
is required. Both vent chamber and the chamber cover can be
heat-sealed along the battery cover in a single heat-sealing
operation.
Fig. 1 shows the battery according to the present
invention in the upright position. In Fig. 6, the battery is
tilted by 90° to lie on one of its shorter sides. In this
position, the electrolyte in each set of three cell
compartments C1-C3 and C4-C6 moves downwards, leaving the
chambers empty. Since each parallel vent line/vent cap is
connected with a respective empty chamber, there is ro
possibility of acid leakage through the vent cap.
Further, central blockage of the common vent line ty
wall 7 prevents transfer of electrolyte from upper cells C1-
C3 to lower cells C4-C6. As a result, with the battery in
this position shown in Fig. 6, when the battery is brought
back to its original upright position shown in Fig. 1, there
is only a negligible cell-to-cell variation in the levels cf
electrolyte. Thus there is a substantial improvement in
minimizing the cell-to-cell variation in the electrolyte
levels even after tilting the battery by 90° to lie on one cf
its shorter sides, as compared to conventional side-vented
batteries having a common vent line through the battery
cover. In fact, in the latter case, significant variation in
the cell-to-cell electrolyte levels does occur, due to
appreciable transfer of electrolyte from the upper cells to
the lower cells when the battery is lying on the shorter
side.
In Fig. 7, the battery of the present invention is shown
to be lying on its back side. In this position, the parallel
vent lines 14 and 15 are barely covered with the electrolyte.
However, hydraulic pressure in this position is too small to
traverse vertically upwards to break the resistance to the
flow of electrolyte through the vent cap 18 and the gas
filter 20. As a result no leakage of electrolyte occurs in
this position for several hours. Further, due to air-lock,
after the battery is tilted to lie on its back side, on its
front side or in the inverted position, there is resistance
to electrolyte leakage for a considerable length of time.
Fig. 8 shows the battery lying on its front side.
Here too, it can be seen that maximum electrolyte level is
below the parallel vent lines 14 and 15. So, there is no
chance of electrolyte leakage when the battery is tilted to
this position.
In the inverted position, an air lock develops. This;
prevents leakage of electrolyte through the vent cap 18 and
filter 19. So, in this position also, no electrolyte leakage
occurs for several hours.
In the present invention, the gas filter is preferably a
water-repellant microporous filter having a grain size of
approximately 70 microns. This is made of plastic alloy and
treated to exhibit water-repellant characteristics. By this,
substantial resistance to leakage of electrolyte through vert
hole can be achieved.
Hence, the present invention discloses a highly leek
resistant battery in all directions. More importantly, this
feature has been achieved in a relatively simple and a cosit
effective manner. Furthermore, according to the present
invention, most of the electrolyte is retained in thez.r
respective cells during the battery rotation or tilt, whereas
in most other leak resistant designs, a substantial amount of
electrolyte is allowed to flow out of the cell in the spa :e
available between the lower lid and the upper lid. Also, In
a conventional side/central gas venting design, a substantial
transfer of electrolyte takes place from the upper cells to
the lower cells when rotated upto 90° along the side face.
However, the present invention helps to provide for the
retention of the electrolyte of each cell in its respective
compartment during rotation and tilt upto 90° on either sice.
The invention has been described with reference to the
preferred embodiments, but, it covers all improvements c.nd
modifications coming within the scope of the invention as
claimed.
WE CLAIM:
1. A multi-cell leak-resistant automotive battery
comprising:
a housing containing cells having filling plugs;
a battery cover heat-sealed to the upper open end of
said housing and having filling holes overlying
respective said cells;
terminals mounted on said battery cover and connected ;o
said cells;
and optionally charge indicator mounted on said battery
cover;
characterised in that,
at least one partition wall is provided in the batte::y
cover to divide the battery cover into at least two vent
chambers, each vent chamber overlying a set of sa:_d
cells, to prevent flow of electrolyte from one set of
cells to an adjacent set of cells when the battery :.s
tilted;
a common vent line in the battery cover to connect the
spaces above the cells in each set of cells, each said
common vent line being sealed at one end and connected
at its other end through each said vent chamber to one end of a
respective parallel vent line, and each said parallel
vent line having at its other end a vent cap assembly
which permits escape of vented gases from the cells in
each set.
2. Battery as claimed in claim 1, wherein said commcn
vent line in each vent chamber is sealed at said one end
by means of a vent stop extending through the battery-
cover into the vent hole of the first cell of each set.
3. Battery as claimed in claim 1 or 2, wherein £:aid
vent cap assembly comprises a vent cap fitted to said
other end of the parallel vent line, and a gas filter
attached to the vent cap for allowing the vented gas to
escape.
4. Battery as claimed in claim 3, wherein said vent
cap has a vent hole provided on the inlet side of the
vent cap, a first vertical hole extending upwards to the
outer periphery of the vent cap and in communication
with said vent hole, a helical path for passage of
vented gases provided on the outer periphery of the vent
cap and connected at one end to said first vertical
hole, a second hole connected to said helical path at
other end of the helical path, said second vertical hDle
extending downwards to the centre at the exit side of
the vent cap so as to be in communication with said
filter.
5. Battery as claimed in claim 3 or 4, wherein said
gas filter is a water-repellant microporous gas filte::.
6. Battery as claimed in claim 5, wherein said
microporous filter has a grain size of about 70 microns.
7. Battery as claimed in any of claims 3 to 6, wheroin
said gas filter attached to the vent cap is covered by
means of a filter cover having a hole for escape of
vented gas.
8. Battery as claimed in any of claims 1 to 7, wherein
each said vent chamber is provided with a chamber covei
press-fitted to it, said vent chamber and chamber covet
being heat sealed to the battery cover.
9. Battery as claimed in any of claims 1 to 8, wherein
each side wall of the housing is provided with a honey
comb structure*
10. A multi-cell leak-resistant automotive battery
substantially as herein described, particularly with reference to the
accompanying drawings.

There is disclosed a multi-cell leak-resistant automotive
battery comprising :
a housing (1) containing cells (C1 to C6) having filling plugs
(3) and a battery cover (2) heat-sealed to its upper open end;
terminals (T1, T2) mounted on said battery cover and connected to
said cells; and optionally charge indicator (CI) mounted on said
battery cover; wherein, at least one partition wall (7) is provided
in the battery cover to divide the battery cover into at least two
vent chambers (22) such that, each vent chamber overlies a set of
said cells (C1 to C3 and C4 to C6) , and a common vent line (VLl, VL2)
is provided in the battery cover to connect the spaces above the
cells in each set of cells, and each said common vent line is sealed
at one end (8'/13') and connected at its other end to one end of a
respective parallel vent line (14/15) and the latter having at its
other end a vent cap assembly (16) which permits escape of vented
gases from the cells in each set.